The invention relates to the technical field of
biomass energy utilization, in particular to a method for producing
biogas by
biomass fermentation, which comprises the following steps: pretreating raw materials, collecting agricultural wastes,
forestry residues, organic household garbage and other
biomass raw materials, sorting and crushing the biomass raw materials until the particle size is 1-3mm, putting the biomass raw materials into a soaking
pool and adding
biogas slurry for soaking, adding a compound
enzyme preparation, and stirring and soaking for 12-24 hours at 30-40 DEG C; draining the pretreated raw materials, inoculating microbial
flora, and transferring into an anaerobic
fermentation tank; in the initial stage of
fermentation, the temperature in the tank is 28-32 DEG C, the pH value is 6.5-7.0 and is kept anaerobic, after the gas
production rate is increased, the temperature is adjusted to 35-38 DEG C, the pH value is 7.0-7.2, and a
buffering agent is added in good time. According to the method, the biomass raw materials are subjected to fine pretreatment, so that complex organic components in the biomass raw materials can be fully decomposed, more organic matters which are originally difficult to utilize by microorganisms are converted into fermentable substrates, the gas production efficiency is remarkably improved, and compared with a traditional method, the
biogas yield can be remarkably increased.